1. Field of the Invention
The present invention relates to an apparatus for manufacturing a semiconductor device, and more particularly, to a dry etching apparatus.
2. Description of the Related Art
A dry etching apparatus uses plasma to carry out various processes in the manufacturing of a semiconductor device. In a dry etching process, a reaction gas is injected into the dry etching apparatus and external power having the frequency of a radio wave is applied to a silicon cathode and an anode of the dry etching apparatus. The energy of electrons accelerated by an RF electric field formed between the cathode and the anode is increased as the electrons elastically collide repeatedly against molecules of the reaction gas. Then, the highly energized electrons collide non-elastically with the molecules of the reaction gas whereby the molecules of the reaction gas are ionized and excited to generate plasma. Negatively charged plasma gases flow to the anode due to a difference in potential between the cathode and the anode. There, the plasma reacts with a wafer located on the anode to generate a material having a high vapor pressure and a volatile material, to thereby etch the wafer.
If the dry etching process described above is to be performed accurately and effectively, the plasma stream must be confined to the wafer supported on the anode and impurities must be suppressed.
However, an examination of a conventional dry etching apparatus (FIG. 1) reveals that sunflower-shaped particles of a polymer and particle contaminants 30 are deposited on an aluminum ring 14 extending along the periphery of an electrostatic chuck (ESC) 12 provided in the lower portion 10 of a processing chamber of the apparatus, and on a plasma confinement ring 24 supporting a silicon cathode 22 in an upper portion 20 of the processing chamber. The aluminum ring 14 is provided to enhance the uniformity of the plasma density, whereas the confinement ring 24 is provided to confine the plasma stream to the area of the wafer.
The present inventor has determined that the deposition of the polymer and of the particle contaminants 30 are caused by occurrences of micro-arcing between screws 26, which fix the confinement ring 24 in place, and the aluminum ring 14 extending along the periphery of the electrostatic chuck 12. The micro-arcing acts at openings for air stream control which are formed in the silicon cathode 22 and an aluminum baffle, mounted on the silicon cathode 22, to control the flow of gas. The particles of silicon or aluminum which are produced as a result of the micro-arcing contaminate the wafer during the dry etching process. Also, the plasma confinement ring 24 does not completely confine the plasma stream to just the area of the wafer. Rather, the plasma diffuses onto the aluminum ring 14. There, some of the plasma combines with the particle contaminants. The plasma and the plasma combined with the particle contaminants are burned by the micro-arcing to form the sunflower-shaped polymer and particles 30 shown in FIG. 1.
The contamination of the wafer, and the presence of the polymer and particle contaminants 30 adversely affects the dry etching process to the point where the yield of satisfactorily etched products is below expectations.